Alternative method for determining leaf CO₂ assimilation without gas exchange measurements: Performance, comparison...

Area of Science:

• Plant Physiology
• Photosynthesis Research
• Remote Sensing Applications

Background:

• Accurate measurement of leaf CO2 assimilation rate (An) is crucial for understanding plant responses to environmental changes.
• Traditional gas exchange methods are labor-intensive and not suitable for large-scale proximal or remote sensing.
• Existing remote sensing approaches often struggle with accuracy and require complex calibration.

Purpose of the Study:

• To develop and validate an alternative method for estimating leaf CO2 assimilation rate (An) using proximal and remote sensing techniques.
• To integrate the Farquhar-von Caemmerer-Berry photosynthesis model with mechanistic light reaction (MLR) theory and leaf energy balance (EB) analysis.
• To assess the model's performance across different plant species and environmental conditions.

Main Methods:

• Combined the Farquhar-von Caemmerer-Berry model with MLR theory and EB analysis.
• Utilized chlorophyll fluorescence (proximal or sun-induced) and spectral reflectance to estimate electron transport rate (J).
• Employed leaf temperature to directly estimate stomatal conductance via the EB equation.

Main Results:

• The MLR-EB model successfully estimated An variations in wheat and soybean, including midday depression.
• Sensitivity analysis highlighted the critical role of leaf boundary layer conductance (gb) in the model's performance.
• The model demonstrated potential for reducing uncertainties in photosynthesis assessment when gas exchange data is absent.

Conclusions:

• The MLR-EB model offers a viable alternative for estimating leaf CO2 assimilation rate without direct gas exchange measurements.
• Accurate estimation of leaf boundary layer conductance (gb) is essential for the model's reliability.
• This approach enhances the applicability of photosynthesis assessment in proximal and remote sensing contexts.